Reply to von Reyn and Horsburgh

Abstract

The study by Muñoz et al [1] demonstrates that the need for treatment of healthy household contacts of active tuberculosis can be safely reduced by 20% when an interferon γ release assay is used to exclude false-positive tuberculin skin test (TST) results. Because the study was conducted in Spain, 28% of trial participants had been previously immunized with Bacille Calmette Guerin (BCG) vaccine, a factor that seemed to be the predominant cause of false-positive TST results. The authors surmise that the remaining proportion of false-positive results may have been due to exposure to nontuberculous mycobacteria (NTM).